Glass shrouds surrounding light source chambers have been employed as explosion and implosion protection devices; selective radiation blockers; and for chamber isothermalization. Mounting of the shrouds has presented numerous problems. U.S. Pat. No. 2,087,745 suggests mounting a shroud by attachment to the outer envelope, which requires that the shroud material and the outer envelope material be the same. U.S. Pat. No. 2,116,720 mounts and positions a shroud by means of helical springs. This technique allows different materials for the shroud and outer envelope but lacks in stability, particularly in a longitudinal direction. U.S. Pat. No. 4,935,668 teaches shroud formation of the same material as the light source chamber with attachment thereto or, alternatively, a shroud of a different material with attachment occurring to the lead-in wires. U.S. Pat. No. 5,252,885 discloses a shroud mounting frame attached to the stem lead at one end of the outer envelope and a button or dimple formed at an opposite end of the outer envelope. U.S. Pat. No. 5,363,007 teaches mounting of a shroud by means of a second pinch seal. U.S. Pat. No. 5,388,034 discloses a light source chamber having a shroud mounted to extensions thereof wherein the chamber and the shroud are of the same material (necessary to match the thermal expansion requirements). U.S. Pat. No. 5,406,165 teaches mounting the shroud to the exhaust tubulation of the light source chamber. This technique requires also that the shroud and chamber material be the same.